A substrate-referenced data-conversion architecture

A substrate-referenced (SR) data-conversion architecture that operates with widely varying single polarity and or bipolar power supplies has been developed. By using well-established analog circuit design techniques and a novel substrate-referenced level-shifting scheme, digital switching noise on the noisiest power supply (V/sub dd/ in p-well CMOS) appears to the analog subsystem as a common-mode signal that is substantially rejected. Substrate-referenced successive-approximation weighted-capacitor analog-to-digital (A/D) converters have been implemented in p-well CMOS technology for several VLSI mixed-mode applications. A conventional ground-referenced converter was also integrated in the same technology for one specific application. With identical static logic circuitry on both chips, the SR architecture exhibited significantly higher accuracy than the conventional architecture.<
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